Magnetic carrier, two-component developer, development method, development device and image forming apparatus of electrophotography

Abstract

A two-component developer including toner and magnetic carriers is provided. The two-component developer is characterized in that when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material, the number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member.

1. A two-component developer for developing an electrostatic latent image, comprising:
 toner; and 
 magnetic carriers, 
 wherein when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material, a number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     2. A two-component developer for developing an electrostatic latent image, comprising:
 toner; and 
 magnetic carriers, 
 wherein in a development device including a developer bearing member having a magnetic field generation device inside thereof and bearing the two-component developer thereupon and a developer regulation member regulating a thickness of a layer of the two-component developer borne on the developer bearing member and in which a distance between the developer bearing member and the developer regulation member is about 0.7 mm and a distance between the developer bearing member and a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material is about 0.35 mm, when a magnetic brush formed on the developer bearing member is caused to rub a surface of the quasi-photoconductor by rotating the quasi-photoconductor at a linear velocity of 245 mm/sec and the development sleeve at a linear velocity of 515 mm/sec, and a DC voltage of 450V superimposed with an AC voltage of 9 kHz in frequency and 900V in Vpp is applied between the developer bearing member and the quasi-photoconductor, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     3. The two-component developer according to  claim 1 , wherein a dynamic resistance value of the two-component developer in an electric field intensity of 10 kV/cm is between 1.0×10 10 Ωcm and 1.0×10 12 Ωcm, and dielectric breakdown is not caused in the two-component developer in an electric field intensity of 27 kV/cm or smaller. 
   
   
     4. The two-component developer according to  claim 2 , wherein a dynamic resistance value of the two-component developer in an electric field intensity of 10 kV/cm is between 1.0×10 10 Ωcm and 1.0×10 12 Ωcm, and dielectric breakdown is not caused in the two-component developer in an electric field intensity of 27 kV/cm or smaller. 
   
   
     5. The two-component developer according to  claim 1 , wherein a weight-average particle diameter of the magnetic carriers is between 25 μm and 45 μm. 
   
   
     6. The two-component developer according to  claim 2 , wherein a weight-average particle diameter of the magnetic carriers is between 25 μm and 45 μm. 
   
   
     7. The two-component developer according to  claim 1 , wherein a magnetization intensity of the magnetic carriers in a magnetic field of 1 kOe is between 60 emu/g and 80 emu/g. 
   
   
     8. The two-component developer according to  claim 2 , wherein a magnetization intensity of the magnetic carriers in a magnetic field of 1 kOe is between 60 emu/g and 80 emu/g. 
   
   
     9. The two-component developer according to  claim 1 , wherein a density of the toner is between 3 wt % and 15 wt %. 
   
   
     10. The two-component developer according to  claim 2 , wherein a density of the toner is between 3 wt % and 15 wt %. 
   
   
     11. A magnetic carrier for use in a two-component developer developing an electrostatic latent image,
 wherein when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material, a number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member, and 
 wherein a weight-average particle diameter of the magnetic carrier is between 25 μm and 45 μm. 
 
   
   
     12. A magnetic carrier for use in a two-component developer for developing an electrostatic latent image,
 wherein in a development device including a developer bearing member having a magnetic field generation device inside thereof and bearing the two-component developer thereupon and a developer regulation member regulating a thickness of a layer of the two-component developer borne on the developer bearing member and in which a distance between the developer bearing member and the developer regulation member is about 0.7 mm and a distance between the developer bearing member and a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material is about 0.35 mm, when a magnetic brush formed on the developer bearing member is caused to rub a surface of the quasi-photoconductor by rotating the quasi-photoconductor at a linear velocity of 245 mm/sec and the development sleeve at a linear velocity of 515 mm/sec, and a DC voltage of 450V superimposed with an AC voltage of 9 kHz in frequency and 900V in Vpp is applied between the developer bearing member and the quasi-photoconductor, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member, and 
 wherein a weight-average particle diameter of the magnetic carrier is between 25 μm and 45 μm. 
 
   
   
     13. The magnetic carrier according to  claim 11 , wherein a magnetization intensity of the magnetic carrier in a magnetic field of 1 kOe is between 60 emu/g and 8 emu/g. 
   
   
     14. The magnetic carrier according to  claim 12 , wherein a magnetization intensity of the magnetic carrier in a magnetic field of 1 kOe is between 60 emu/g and 80 emu/g. 
   
   
     15. A development method of developing an electrostatic latent image on a surface of an image bearing member, the method comprising:
 bearing a two-component developer including toner and magnetic carriers on a developer bearing member arranged to oppose the image bearing member and including a magnetic field generation device inside thereof; 
 conveying the two-component developer borne on the developer bearing member to a development area formed between the developer bearing member and the image bearing member; and 
 causing a magnetic brush formed on the developer bearing member to rub a surface of the image bearing member to develop the electrostatic latent image on the surface of the image bearing member, 
 wherein when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     16. A development method of developing an electrostatic latent image on a surface of an image bearing member, the method comprising:
 bearing a two-component developer including toner and magnetic carriers on a developer bearing member arranged to oppose the image bearing member and including a magnetic field generation device inside thereof; 
 conveying the two-component developer borne on the developer bearing member to a development area formed between the developer bearing member and the image bearing member; and 
 causing a magnetic brush formed on the developer bearing member to rub a surface of the image bearing member to develop the electrostatic latent image on the surface of the image bearing member, 
 wherein a development device including a developer bearing member having a magnetic field generation device inside thereof and bearing the two-component developer thereupon and a developer regulation member regulating a thickness of a layer of the two-component developer borne on the developer bearing member and in which a distance between the developer bearing member and the developer regulation member is about 0.7 mm and a distance between the developer bearing member and a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material is about 0.35 mm, when the magnetic brush formed on the developer bearing member is caused to rub a surface of the quasi-photoconductor by rotating the quasi-photoconductor at a linear velocity of 245 mm/sec and the development sleeve at a linear velocity of 515 mm/sec, and a DC voltage of 450V superimposed with an AC voltage of 9 kHz in frequency and 900V in Vpp is applied between the developer bearing member and the quasi-photoconductor, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     17. The development method according to  claim 15 , wherein the electrostatic latent image on the surface of the image bearing member is developed with loose toner caused to separate from the magnetic carriers when ears of the magnetic brush in which the magnetic carriers have gathered rise in the development area. 
   
   
     18. The development method according to  claim 16 , wherein the electrostatic latent image on the surface of the image bearing member is developed with loose toner caused to separate from the magnetic carriers when ears of the magnetic brush in which the magnetic carriers have gathered rise in the development area. 
   
   
     19. The development method according to  claim 15 , wherein the electrostatic latent image on the surface of the image bearing member is developed by causing loose toner to be separated from the magnetic carriers when ears of the magnetic brush in which the magnetic carriers have gathered rise in the development area to move to the electrostatic latent image on the surface of the image bearing member, and thereafter by movement of toner to the image bearing member from the magnetic carriers and movement of toner from the image bearing member to the magnetic carriers. 
   
   
     20. The development method according to  claim 16 , wherein the electrostatic latent image on the surface of the image bearing member is developed by causing loose toner to be separated from the magnetic carriers when ears of the magnetic brush in which the magnetic carriers have gathered rise in the development area to move to the electrostatic latent image on the surface of the image bearing member, and thereafter by movement of toner to the image bearing member from the magnetic carriers and movement of toner from the image bearing member to the magnetic carriers. 
   
   
     21. The development method according to  claim 15 , wherein an electric field formed between the image bearing member and the developer bearing member is an alternating electric field. 
   
   
     22. The development method according to  claim 16 , wherein an electric field formed between the image bearing member and the developer bearing member is an alternating electric field. 
   
   
     23. A development device for developing an electrostatic latent image on an image bearing member, comprising:
 a developer bearing member arranged to oppose the image bearing member and including a magnetic field generation device inside thereof; and 
 a rotation drive device configured to rotate the developer bearing member, 
 wherein the developer bearing member bears a two-component developer including toner and magnetic carriers to convey the two-component developer to a development area formed between the developer bearing member and the image bearing member, and a magnetic brush formed on the developer bearing member is caused to rub a surface of the image bearing member, thereby developing the electrostatic latent image on the image bearing member, and 
 wherein when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material, a number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     24. A development device developing an electrostatic latent image on an image bearing member, comprising:
 a developer bearing member arranged to oppose the image bearing member and including a magnetic field generation device inside thereof; and 
 a rotation drive device configured to rotate the developer bearing member, 
 wherein the developer bearing member bears a two-component developer including toner and magnetic carriers to convey the two-component developer to a development area formed between the developer bearing member and the image bearing member, and a magnetic brush formed on the developer bearing member is caused to rub a surface of the image bearing member, thereby developing the electrostatic latent image on the image bearing member, and 
 wherein in a development device including a developer bearing member having a magnetic field generation device inside thereof and bearing the two-component developer thereupon and a developer regulation member regulating a thickness of a layer of the two-component developer borne on the developer bearing member and in which a distance between the developer bearing member and the developer regulation member is about 0.7 mm and a distance between the developer bearing member and a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material is about 0.3 5 mm, when a magnetic brush formed on the developer bearing member is caused to rub a surface of the quasi-photoconductor by rotating the quasi-photoconductor at a linear velocity of 245 mm/sec and the development sleeve at a linear velocity of 515 mm/sec, and a DC voltage of 450V superimposed with an AC voltage of 9 kHz in frequency and 900V in Vpp is applied between the developer bearing member and the quasi-photoconductor, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     25. The development device according to  claim 23 , wherein the electrostatic latent image on the surface of the image bearing member is developed with loose toner caused to separate from the magnetic carriers when ears of the magnetic brush in which the magnetic carries have gathered rise in the development area. 
   
   
     26. The development device according to  claim 24 , wherein the electrostatic latent image on the surface of the image bearing member is developed with loose toner caused to separate from the magnetic carriers when ears of the magnetic brush in which the magnetic carries have gathered rise in the development area. 
   
   
     27. An image forming apparatus, comprising:
 an image bearing member; 
 a charge device configured to charge a surface of the image bearing member; 
 an exposure device configured to expose the surface of the image bearing member to form a latent image thereupon; 
 a development device configured to supply toner to the latent image on the image bearing member to develop the latent image with toner into a toner image; and 
 a transfer device configured to transfer the toner image on the surface of the image bearing member to a transfer member, 
 wherein the development device includes a developer bearing member arranged to oppose the image bearing member and having a magnetic field generation device inside thereof, 
 wherein the developer bearing member bears a two-component developer including toner and magnetic carriers to convey the two-component developer to a development area formed between the developer bearing member and the image bearing member, and a magnetic brush formed on the developer bearing member is caused to rub a surface of the image bearing member, thereby developing the electrostatic latent image on the image bearing member, and 
 wherein when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 μtm thick layer of tetrafluoroethylene resin is provided to a conductive material, a number of times of light emission occurring due to partial conduction in a magnetic brush formed on the developer bearing member is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     28. An image forming apparatus, comprising:
 an image bearing member; 
 a charge device configured to charge a surface of the image bearing member; 
 an exposure device configured to expose the surface of the image bearing member to form a latent image thereupon; 
 a development device configured to supply toner to the latent image on the image bearing member to develop the latent image with toner into a toner image; and 
 a transfer device configured to transfer the toner image on the surface of the image bearing member to a transfer member, 
 wherein the development device includes a developer bearing member arranged to oppose the image bearing member and having a magnetic field generation device inside thereof, 
 wherein the developer bearing member bears a two-component developer including toner and magnetic carriers to convey the two-component developer to a development area formed between the developer bearing member and the image bearing member, and a magnetic brush formed on the developer bearing member is caused to rub a surface of the image bearing member, thereby developing the electrostatic latent image on the image bearing member, and 
 wherein the two-component developer is characterized in that in a development device including a developer bearing member having a magnetic field generation device inside thereof and bearing the two-component developer thereupon and a developer regulation member regulating a thickness of a layer of the two-component developer borne on the developer bearing member and in which a distance between the developer bearing member and the developer regulation member is about 0.7 mm and a distance between the developer bearing member and a quasi-photoconductor in which a 10 μm thick layer of tetrafluoroethylene resin is provided to a conductive material is about 0.35 mm, when a magnetic brush formed on the developer bearing member is caused to rub a surface of the quasi-photoconductor by rotating the quasi-photoconductor at a linear velocity of 245 mm/sec and the development sleeve at a linear velocity of 515 mm/sec, and a DC voltage of 450V superimposed with an AC voltage of 9 kHz in frequency and 900V in Vpp is applied between the developer bearing member and the quasi-photoconductor, a number of times of light emission occurring in the magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     29. An image forming apparatus, comprising:
 a quasi-photoconductor having a 10 μm thick layer of tetrafluoroethylene resin provided to a conductive material; and 
 a developer bearing member, 
 wherein the developer bearing member is configured to bear two-component developer, the two-component developer including toner and magnetic carriers, and 
 wherein the developer bearing member includes a magnetic brush formed on a surface of the developer bearing member, such that a number of times of light emission occurring in the magnetic brush is less than or equal to 10 times per second at an observation cross section perpendicular relative to a rotation axis of the developer bearing member. 
 
   
   
     30. An apparatus for developing an electrostatic latent image, the apparatus comprising:
 first means for bearing a two-component developer including toner and magnetic carriers, arranged to oppose a second means for bearing an image; 
 means for conveying the two-component developer from the first means for bearing to a development area between the first means for bearing and the second means for bearing; 
 means for rubbing a magnetic brush from the first means for bearing against a surface of the second means for bearing; and 
 means for quasi-photoconducting including an approximately 10 μm thick layer of tetrafluoroethylene resin and a conductive material, 
 wherein a number of times of light emission occurring in the magnetic brush is less than or equal to 10 times per section at an observation cross section perpendicular to a rotation axis of the first means for bearing.